1. Field of the Invention
The invention relates to a method, for dicing a wafer, in which a wafer having a plurality of electronic circuits formed at one side thereof is diced, to thereby separate it into the plurality of semiconductor chips.
2. Description of the Related Art
Recent electronic instruments are required to be increasingly small and light and, accordingly, semiconductor packages used in an electronic instrument and thus semiconductor chips incorporated in semiconductor packages are expected to be made small and light. This is accompanied by the development of demand that a wafer, prior to its dicing, and from which semiconductor chips are obtained, has a very small thickness, such as of 50 micrometers or smaller.
When a wafer, such as a silicon wafer, is formed so as to have a very small thickness, such as 50 micrometers or smaller, problems can arise. For example, such a thin wafer can crack during the steps from the formation to the dicing thereof.
For this reason, various ideas of handling and dicing a thin wafer, without causing it to be damaged, have been proposed.
For example, as described in JP 2000-306875 A, the side of a wafer having circuits formed, to which a dicing tape is applied, is sucked onto a vacuum chuck table through the dicing tape, and the wafer is thinned by grinding the back side of the wafer opposed to the circuit-forming side (FIG. 9 and paragraphs 0031–0033 of JP 2000-306875 A). Subsequently, the wafer is diced by irradiating the back side thereof with infrared rays penetrating through the wafer, at the scribing line (marking) formed along the dicing line for the wafer, observing the scribing line by the use of an infrared camera, and controlling and moving a dicing saw along the scribing line (FIGS. 10 and 11 and paragraphs 0037–0038 of JP 2000-306875 A).
According to the method described in JP 2000-306875 A, operations for grinding a wafer to make it thinner, the wafer having a protective tape applied to the circuit-forming side thereof for the protection during the grinding, then removing the protective tape, and placing the wafer on a dicing tape (FIG. 4 and paragraphs 0008–0010 of JP 2000-306875 A), are not necessary, and effects, such as prevention of crack of the thin wafer, can be obtained (paragraph 0042 of JP 2000-306875 A).
In the above prior art, there is also a method in which the wafer is diced by irradiating it with a laser beam along the dicing line to melt the wafer, in place of the use of the dicing saw.
The above prior methods have a problem that a dicing saw, which is made, in general, of a rotating diamond blade or the like, is used in the step of dicing, and cracks, breaks of the edges, flaws or the like can be developed in a wafer (or diced semiconductor chips), resulting in the deterioration in quality and production yield of semiconductor chips.
The above prior methods also have a problem that an image pickup means, such as an infrared camera, capable of picking up special transmitted light from the wafer, such as infrared rays, is needed, leading to the increased cost of equipment.
Further, the prior method, in which a wafer is diced by cutting it using a laser beam in place of a dicing saw, has a problem that diced chips may have protuberances (so-called debris) at their cut edges due to the melting of the cut portions of the wafer by the laser beam, or circuits in the wafer may be damaged due to heat, resulting in the deterioration in quality and production yield of semiconductor chips.